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Narrowband power line communications (NB-PLC) systems operating in the frequency range 3-500 kHz were developed and used in the past few decades for telecommunications, metering, control, and automation. Recently, OFDM-based NB-PLC solutions known as G3 and PRIME came to the market after a long monopoly of single-carrier technologies, offering higher bit rates, robustness, and flexibility, which are vital for smart grid applications. However, it was realized that an international standard is important to ensure worldwide interoperable products and avoid market fragmentation. In the beginning of 2010, the IEEE Standards Association and ITU-T started standardization of NBPLC technologies based on OFDM, launching the P1901.2 and G.hnem projects, respectively. This article gives a technical overview of the ITU-T G.hnem standard, which defines a unified NB-PLC OFDM-based technology targeting multiple smart grid applications: smart metering, distributed automation, in-home energy management, generic home automation, car charging, and others, using IPv6 as the main networking protocol. ITU-T Recommendations G.9955 (G.hnem physical layer) and G.9956 (G.hnem data link layer) were consented for approval in February 2011; their final approval is expected in December 2011.